Effect of Laser Welding Sequence on Residual Stress and Deformation of Titanium Alloy U-beam

The TC4 titanium alloy U-beam was welded by 1 panel and 2 webs, the welding of the two long welds was carried out by using laser self-melting welding. In order to study the effect of laser welding sequence on the residual stress and deformation of the U-beam, the stress and deformation of the U-beam under different welding sequences were compared and analyzed by using finite element simulation and the heat source model combined Gaussian surface heat source and cylindrical heat source. The results show that the distribution of residual stress and deformation of the U-beam is different under different welding sequences. In the sequential welding scheme of two welds with same direction, the residual stress of the weld in the middle of the U-beam remains stable, and the stress of the position under the other schemes of four welds with segmented welding at the U-beam center decreases. Because the U-beam center position is located at the arc starting or arc ending of the front weld, and it is subjected to the heat treatment of the rear weld, therefore the residual stress is released. The deformation of the sequential welding of two welds with same direction is the largest. For the scheme of sequential welding from the middle to the end at same side and symmetry welding for both sides and the scheme of sequential welding from the center to the end at different sides and symmetry welding for both sides, the maximum deformation is the minimum. Considering the actual welding process, arc striking plates can be set at both ends of the U-beam, which is more conducive to ensuring the weld forming quality. Therefore, the sheme of sequential welding from the center to the end at different sides and symmetry welding for both sides is suitable.